A new, highly potent 1,8‐naphthalimide‐based fluorescence turn‐off chemosensor capable of detecting Cu(II) ions in real‐world water samples

The synthesis of a new 1,8‐naphthalimide‐based fluorescence turn‐off chemosensor for the effective detection of Cu(II) ions is reported. The chemosensor MAST was characterised by mp, Fourier Transform‐infrared (FTIR), ultraviolet‐visible (UV‐vis), fluorescence, 1H‐NMR and 13C‐NMR spectroscopy, and mass spectrometry. After treatment with Cu(II) ions in coexistence with various competitive metal ions in a dimethylsulphoxide (DMSO)/4‐(2‐hydroxyethyl)‐1‐piperazineethanesulphonic acid (HEPES) buffer solution (v/v, 1:1; pH 7.4), the chemosensor demonstrated high selectivity towards Cu(II) ions and a fluorescence quenching of 83.67% was observed. In addition, a good linear response for the chemosensor detecting Cu(II) ions was obtained over the concentration range 0.2–1 μm. The combined results of UV‐vis and fluorescence titrations with the Job plot yielded a 1:1 stoichiometric interaction of the chemosensor with Cu(II) ions. The association constant and detection limit were calculated as 1.37 x 106 m−1 and 1.69 x 10−8 m, respectively. Based on results, the quenching response of MAST towards Cu(II) ions could be ascribed to the reverse‐photoinduced electron transfer (PET) mechanism. Finally, the proposed chemosensor was applied to quantify Cu(II) ions in real‐world water samples and excellent recovery rates of 98–105.8% were obtained.